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SkydiverChris

Starting Issue - Is It My Glow Plugs?

209 posts in this topic

Low pressure fuel pump problem maybe? I have one here that had a cold start problem that you could hear the pump make a slightly off sound and it turned out it was the problem. Do you have any friends with smarts in the area then you can compare the sound?I've been rocking the Brabus with low compression in cylinder #2 and its a pain to start when the engines cold. Do a compression test and rule that out.

Edited by dmoonen

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Not that it's going to get cold enough again to try, but with my old VW and MB (as well as a couple diesel trucks I used to drive), to help it start in the cold I would sometimes cycle the glow plugs 2 or 3 times to warm the head up more. It's a little harder on the battery, glow plugs, and wires but it made a difference.Over time (and use) the wires can lose conductivity, just like spark plug wires.

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@TolsenPossibly, but it is happening right around the freezing point (and sometimes well below). When it's around 0, the car will not start unless I let the glow plugs run their cycle, and that's when the issue isn't occurring. It's the only possible thing that could make sense, but I'm still baffled why it's so intermittent.You may be right, but between everyone in this thread who has the issue, we've literally torn apart the cars (well, Dom did anyways). Parts were replaced, SAM's checked, I bought a Star computer to check it on an ongoing basis, no codes are being thrown. It has to be something that the computer doesn't care about, or doesn't know about which makes me believe it's not a sensor, or any of the computers. The car doesn't know how warm the glow plugs are, it simply runs a time based cycle and relies on engine temperature readings to determine when to shutoff the glow light.The glow plugs (or that system) is the only possible cause and I'm going nuts with this issue.@DmoonenWhat sort of pressure gauge would I need? I have one for my dirt bikes, but I'm guessing that the diesel is a little over 180psi. As for the LP fuel pump, that was my first thought when this thread started, but the car has never stalled, stuttered, etc. And it eventually starts, just not until it's been cranking and had a chance to get some friction head from the pistons.@MarchannaWhen the issue was really prominent this winter, I tried cycling 5 times in a row before cranking. No impact, unfortunately.

Edited by SkydiverChris

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You'll need one that can go up to a higher pressure, most readings I've done on smarts if I recall off the top of my head read around 362 psi you'll need one that has a long reach and has a m10x1 fitting to fit into the glow plug location.

check out this little chart: https://www.uniteddiesel.co.uk/diesel-engine-problems

Edited by dmoonen

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These diesel engines do not depend on glow plugs to start when temperature is above freezing point so the problem is something else.

Yeap! And I performed the test alot of times and the cdi engine could start right up without any wait about the glowplug light until +/- -15c. I seriously doubt that your issue is from your glowplugs system Chris. Make an easy test, measure your crank sensor resistance to the ECM connector when your starting issue occur. ;) Edited by dieselkiki

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What sort of pressure gauge would I need? I have one for my dirt bikes, but I'm guessing that the diesel is a little over 180psi. As for the LP fuel pump, that was my first thought when this thread started, but the car has never stalled, stuttered, etc. And it eventually starts, just not until it's been cranking and had a chance to get some friction head from the pistons.

Chris,You don't need a physical gauge if you have a star machine.There is a page in the star machine that let's you actuate the low pressure fuel pump and it displays the output pressure of the pump.Canman

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Mhm for a compression test you do. The star you can read the fuel quantity and pressures, two separate things :)

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Chris,You don't need a physical gauge if you have a star machine.There is a page in the star machine that let's you actuate the low pressure fuel pump and it displays the output pressure of the pump.Canman

Output pressure of high pressure pump - yes. There is no pressure sensor in low pressure fuel pipes so not possible to read pressure there unless you check with a pressure gauge. Specified pressure is 2 bar. Measured pressure on mine (using multiple gauges since none were calibrated) was 2.5 bar.

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Output pressure of high pressure pump - yes. There is no pressure sensor in low pressure fuel pipes so not possible to read pressure there unless you check with a pressure gauge. Specified pressure is 2 bar. Measured pressure on mine (using multiple gauges since none were calibrated) was 2.5 bar.

Perhaps it uses the same pressure sensor as the high pressure pump.Here is a screen shot of the star machine showing the low pressure pump pressure and fuel temperature.Canmanpost-9481-1398309032_thumb.jpg

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I last checked mine with the Star when I was having starting issues in December during a cold snap, 3.4 Bar and 8°C (same as garage temperature). That is what led me to change the glow plugs.

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So, I figured I'd resurrect this old thread from last year to give an update. My start issue disappeared all summer, then we had a few cold days a couple weeks ago and it reappeared. Since the weather got warm again, I figured I'd get some stuff done while it was still warm out, so here's what I've done in the last week. Some has no relevance to the start issue, but it's all part of the plan...

-New Engine Coolant

-Fresh oil change

-Transmission Oil change

-New glow plugs

-New Injector seals

-New Crank position sensor (Thanks to DieselKiki for his work discovering this)

-EGR Emulator (and soon to be full EGR delete, just waiting on the blanking plate to arrive)

And I'll also be installing a new Intercooler and IC Fan. Fan is failing, and when we did the Crank Sensor at Troy's shop on Saturday, the plastic housing for the IC chewed through the IC. Mercedes wants $472.80+tax.

Anyways...I am eagerly awaiting the cold weather again so I can see if the issue reoccurs. I'll post an update with the results once we're a few weeks into the cold weather.

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No, didn't do a compression test. Reason: 2 of the 3 injectors were actually leaking (soap bubbles), and it was spewing white smoke pretty decently. Now that the injector seals are replaced, along with the injector cleaning, the smoke seems to be much, much less (faint even). Plus, the crank sensor in that guide says it can also cause timing issues and result in unburnt fuel causing white smoke again. Maybe both were on the way out. I'm literally just begging the powers that be, that this fixes the issue.

I simply cannot believe the amount of money I've invested in this car. More than any vehicle I've ever owned, combined, by far, and this is the first vehicle I've ever actually done anything more than the most basic maintenance myself on. God forbid I had to bring this to Mercedes each time. I even bought my own Star computer so I can properly work on it.

I literally just hope nothing else major goes wrong, and my preventative fixes have resolved the start issue.

I still really appreciate everyone's help and all the suggestions in troubleshooting this issue.

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Change the seals first since they're only a couple bucks and do a compression test. That will rule out if its compression related.

Essentially white smoke is caused by raw, un-burnt fuel passing into the exhaust stream

  1. Low cylinder compression
  2. Incorrect fuel injection timing
  3. Defective fuel injectors

So essentially if you change the seals and go a compression test you rule out #1, for #3 you can read the injector quanity VIA star which can tell you the deviaton if its far off the injector is toast, for #2 it could be a mix of a bad injector or crank sensor

Yeah I ended up becoming a pit crew for mine lol.

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Evening,

I finally took some time to go play with the car and here's what I came up with. Unfortunately, I still have no ability to do a compression test due to lack of tools. The details below show injector pressures, RPMs of each cylinder, and injection timing. I'm hoping someone can run the same tests on their car and compare the results. Let me know what you think....

Thank you!

Engine Sensors
Rail Pressure: Varies from about 238-245 BAR
Common Rail
Crankshaft RPM 823-828 RPM
Fuel Injection
Quantity Injected: 5.08mm3
Injection angle Commencement: -2.58 deg KW
Actuation Period of main injection: 0.6ms
Injection angle Start of actuation of preinjection: 14.51 deg KW
Injection time start of actuation of preinjection: 0.4ms
Element Shut off of high pressure pump: 100%
Cylinder-Selective Parameters
Quantity Correction Cyl 1: -0.49
Quantity Correction Cyl 2: +0.34
Quantity Correction Cyl 3: +0.15
Rotation of Cyl 1: 824
Rotation of Cyl 2: 826
Rotation of Cyl 3: 826
Fuel Supply System
Fuel Supply On/Off Ratio (PCV): ~15.75%
Engine Start Data
Injection quantity at engine start varies from 10.43 mm3 to 16.80mm3 to 9.43mm3 across 3 starts
Synchronization Status: Cylinder 1 (never saw anything different)
Boost Pressure Start of actuation of preinjection: 0.98 bar
Exhaust Gas Relevant Data
EGR Positioner 3%
On/OFF ratio of EGR positioner 0%
Specified value EGR positioner 2.69%
Engine Load 0.52%

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Battery showed 10.8 volts on the Scanguage (VERY LOW).

You are very sure that your battery is good now? Fail to comms could be related to undervoltage.

When I want to verify my fuel delivery I crack an injector line (14mm) open a half a turn. Low pressure pump lets a drop or two out, high pressure squirts like a fresh fruit.

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Hey PinHead,

I'm not sure where in the thread you grabbed that from, but I had replaced the battery last year, still occurring. Even then, the car started that day when the battery was completely dead...just not until the car had sat for a couple more hours.

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It was way back somewhere, and the comment about directing heat to the footwell helping your success made me wonder even more. Hopefully with the computer interface you can find the witch!

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Have you tested for bad ground. Try running a jumper lead from battery negative to engine block or transmission.

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If one of the GLowPLug broke off on removing it, can we use a kit like that to remove it without open the engine head ?

http://cdn2.bigcommerce.com/server3000/jtxevi2o/products/49314/images/30418/W900_0199_Glow_Plug_Remover__01876.1393945963.1280.1280.PNG?c=1

It will be bad to have metal inside the cylinder..

Edited by David_18

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That kit looks fairly good. Nowhere near foolproof, the guy being filmed using it was good enough to make it look easy. I have made a lot of threads, removed many broken threaded components, I understand metal-working, I have all the skills. Faced with a broken glowplug I would find that kit great, and succeed.

Without good relevant experience that kit is worse than useless, because it tempts people into making a bad situation worse. I don't want to judge your skills on almost no evidence. Your call. Do you "get" all the steps in that video? Have you drilled out and removed a broken stud successfully?

Re the shavings: Start clean, work clean, vacuum carefully, cross your fingers. Removing the head is indeed less likely to lodge a chip in the turbo, but opens up several more cans of worms, each of which is expensive and risky in it's own way.

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The car have 146k km and 8 winters on it...

Never got the Glow change and i start to have a strange startup problem when the engine is warm (not totally cold) (1-2 hours after shooting it off).

I try to test the Glow with a multimeter, but I can not get a stable reading. i will try later if I can get it right..

I don't want to change it my self if i am sure to not broke it.. :S

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Laser Tools 5205 is very good value for only £100 delivered to your door. Glow plug removal tool kits normally cost £600 +. I agree with Alex, tools like this require some skills and experience.

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